A few things that Pyret gets out of "where" blocks that it's not obvious are easy with just assertions after the function.

- Reporting failures can more easily report context about the function being tested

- Since "where" blocks are actual blocks, we define helper functions and variables inside them that don't need to clutter up the namespace of the current scope

- It's easy to turn the assertions on and off; for example when importing a Pyret module we skip running the checks of that module by default.

- The localized information also plays into our story for type inference (which is work in progress), but starts from the unit tests in the where: block to figure out what the programmer intended for input/output types.

Sure. And so it would in Pyret. It is just some sugar to make it more clear that this code belongs to a particular function. It can also be much more improved and coupled to the 'owner' function, but that's just a simple example of how to make a macro that emulates in part Pyret's inline tests.